Hasil untuk "Cellular telephone services industry. Wireless telephone industry"

Alexane NGHIEN, Marc Pierrot-Deseilligny

Une méthode de mise à plat numérique de plans baguettes (plans papiers de l’Ancien Régime soutenus entre deux baguettes en bois) a été proposée pour aider les Archives Nationales dans leur conservation de patrimoine sous forme numérique. Cette méthode de mise à plat utilise le logiciel de photogrammétrie MicMac (Rupnik et al., 2017). On y réalise ainsi une chaîne de traitements photogrammétrique afin de générer à partir de photographies d’un plan, son maillage triangulé. Un stage de fin d’étude a été réalisé pour adapter cette méthode existante, l’évaluer et la transmettre de façon optimale aux Archives Nationales. Désormais les Archives Nationales utilise cette application particulière de MicMac, ainsi qu’un protocole de photogrammétrie leur permettant de développer des plans anciens.

Yasong Luo, Zhaodong Wu, Chengxu Feng et al.

Active jammers in the form of digital radio frequency memory (DRFM) could produce false targets with a coherence of range and velocity, making it increasingly efficient in interrupting radar systems based on data correlation analysis. By integrating the temporal variability characteristic and mitigating the impact of measurement errors inherent in the radar system, we propose a novel false target recognition methodology for a two-station netted radar utilizing extended Kalman filter (EKF) and the Neyman–Pearson criterion. From the aspects of filtering characteristics and active jammer parameters, the simulation shows that the technique could obtain observable different convergence curves for false targets and is sensitive to velocity or range deception under specific parameters. Moreover, the method exhibits a favorable tolerance for measurement error and an exceptional capability to identify false targets from various directions, considering both radar performance parameters and spatial scale. This outcome highlights the significance of setting specific parameters following countermeasure scenarios and requirements, showcasing its practical value in engineering practice.

Ruihua Ma, He Huang, Xiaoping Li et al.

This paper proposes an integrated decoupling method that improves the flexibility of multiport, multiband antenna design and simplifies the antenna structure. First, a dual-band L-type MIMO antenna with center frequencies of 2.6 GHz and 5.6 GHz is created using the neutralization-line decoupling method and then a dual-band L-type MIMO antenna covering the WiFi spectrum (2.3–2.5 GHz and 4.6–5.6 GHz) is created using the type-T branch decoupling technique. After demonstrating the efficacy of neutralization-line and T-branch decoupling technology for L-type antennas, a four-port L-type MIMO antenna covering 4.4–4.9 GHz, 5.4–6.1 GHz, and 7.0–7.4 GHz is proposed by combining the methods of neutralization-line decoupling, T-branch decoupling, and defected ground structure decoupling. This antenna’s isolation is higher than 20 dB with ECC less than 0.04.

ZheYu Li, JiaHao Zhang, YaXing Li et al.

In interference cancellation, the null at the angle of arrival (AoA) of interference can suppress interference. However, due to the large spacing between array elements and the periodicity of the array, some small nulls at the angles of noninterference are formed inevitably. When the AoA of the desired signal is in these small nulls, they impair the effectiveness of interference cancellation by attenuating the desired signal. This paper proposes the concept of a side null to represent these nulls in the noninterference direction. And the cancellation ratio of the desired signal (SCR) is deduced to quantitatively characterize the side null. The spatial noncooperative interference cancellation model based on the main-auxiliary antenna array is established. Based on this, the SCR is derived to evaluate the amount of desired signal attenuation. Then the simulation, respectively, in two-dimensional plane and three-dimensional space, describes the side null visually. Moreover, the method of side null reduction is discussed by modulation of the array. Finally, the existence of side null and its influence on interference cancellation are verified through the experiments. The results of the simulation and experiment are in good agreement, and both support the theoretical analysis.

S. Prasad Jones Christydass, S. Suresh Kumar, V. S. Nishok et al.

For WLAN/WIMAX applications, a brand-new tree-shaped metamaterial-loaded microstrip antenna is suggested. The reduced ground plane size and 4.4 dielectric constant (r) and 0.02 loss tangent (δ) dielectric are used to manufacture the 15 × 16 × 1.6 mm3 microstrip antenna. Two X-shaped slots are added to achieve the characteristics needed for WIMAX applications at 5.5 GHz. Additionally, a split-ring resonator is added to the structure to increase its bandwidth. It runs for WLAN applications with a center frequency of 5.8 GHz. The proposed structure’s measured impedance bandwidth is 45.39% with SRR and 53.48% without SRR, respectively. The proposed antenna is capable of satisfying the major requirements of modern wireless devices such as multiband operation, compact size, large bandwidth, and planar structure. The best outcomes are attained with the aid of parametric analysis of feed width, ground height, and slot width. All electromagnetic simulations were performed using CST Studio software. The measured results and the simulation agree. The waveguide extraction approach is used to demonstrate the SRR’s permeability property. The suggested antenna had adequate impedance matching, was small, and had a wide bandwidth.

Peter L. Tokarsky

System analysis is a powerful tool for researching modern wireless systems. This includes breaking such systems into parts that make them up and studying how these parts work together. All these parts can be represented as “black boxes” in the form of two-port or multiport networks with the common system of parameters. Antenna is an integral part of any wireless system, so it should be also represented as a two-port network. In this paper, an analytical model of an arbitrary single antenna in the form of a two-port network, whose electrical and noise parameters are described in terms of scattering matrices, is obtained. The initial data for creating the model are the antenna fundamental parameters, viz., the input reflection coefficient and the radiation efficiency. Applications of this model for antenna analysis operating in the transmitting, receiving, and scattering modes are demonstrated. A numerical example using the antenna scattering matrix for computer simulation of a wireless connection is given.

Lijian Xin, Yong Li, Hao Sun et al.

This paper proposes an over-the-air (OTA) testing setup for millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) equipment using cascaded amplitude and phase modulation (APM) network and channel emulator. Compared with the existing test setup with mechanical switch, the proposed testing setup enables more accurate reconstruction of the radio channel environment under the multiprobe anechoic chamber (MPAC) setup without increasing the number of channel emulators (CEs) to control the system cost. The constructed MPAC testing setup for mmWave and massive MIMO equipment is composed of an anechoic chamber, a sectored probe wall containing a number of probes, an APM network, a fading channel emulator, and a user emulator (UE). In this paper, the structural model and the performance advantages of the proposed radiated testing setup are described, and a fully connected APM network for radiated testing is more prominent than the existing switch. Moreover, the angular spectrum is selected as the performance metric for the reconstructed channel. The ability of the proposed system to reconstruct the power angular spectrum (PAS) of the target channel is studied under both static and dynamic channel models, which can reflect the performance of beamforming procedures of the massive MIMO antenna arrays, e.g., beam acquisition, tracking, and refinement. The simulation results for angular spectrum support the superiority of the proposed OTA testing setup. Furthermore, the simulations for average channel capacity also show that radiated testing setup using cascaded APM network and channel emulator is valid.

Noor Gul, Ijaz Mansoor Qureshi, Atif Elahi et al.

In cognitive radio network (CRN), secondary users (SUs) try to sense and utilize the vacant spectrum of the legitimate primary user (PU) in an efficient manner. The process of cooperation among SUs makes the sensing more authentic with minimum disturbance to the PU in achieving maximum utilization of the vacant spectrum. One problem in cooperative spectrum sensing (CSS) is the occurrence of malicious users (MUs) sending false data to the fusion center (FC). In this paper, the FC takes a global decision based on the hard binary decisions received from all SUs. Genetic algorithm (GA) using one-to-many neighbor distance along with z-score as a fitness function is used for the identification of accurate sensing information in the presence of MUs. The proposed scheme is able to avoid the effect of MUs in CSS without identification of MUs. Four types of abnormal SUs, opposite malicious user (OMU), random opposite malicious user (ROMU), always yes malicious user (AYMU), and always no malicious user (ANMU), are discussed in this paper. Simulation results show that the proposed hard fusion scheme has surpassed the existing hard fusion scheme, equal gain combination (EGC), and maximum gain combination (MGC) schemes by employing GA.

Giulia Mansutti, Francesco Rigobello, Sajid M. Asif et al.

The projection method (PM) is a simple and low-cost pattern recovery technique that already proved its effectiveness in retrieving the radiation properties of different types of arrays that change shape in time. However, when dealing with deformable beam-tilting arrays, this method requires to compute new compensating phase shifts every time that the main lobe is steered, since these shifts depend on both the deformation geometry and the steering angle. This tight requirement causes additional signal processing and complicates the prediction of the array behavior, especially if the deformation geometry is not a priori known: this can be an issue since the PM is mainly used for simple and low-cost systems. In this letter, we propose a simplification of this technique for beam-tilting arrays that requires only basic signal processing. In fact the phase shifts that we use are the sum of two components: one can be directly extracted from strain sensor data that measure surface deformation and the other one can be precomputed according to basic antenna theory. The effectiveness of our approach has been tested on two antennas: a 4 × 4 array (trough full-wave simulations and measurements) and on an 8 × 8 array (trough full-wave simulations) placed on a doubly wedge-shaped surface with a beam tilt up to 40 degrees.

Jiaqi Song, Haihong Tao, Jian Xie et al.

Based on a dual-size shift invariance sparse linear array, this paper presents a novel algorithm for the localization of mixed far-field and near-field sources. First, by constructing a cumulant matrix with only direction-of-arrival (DOA) information, the proposed algorithm decouples the DOA estimation from the range estimation. The cumulant-domain quarter-wavelength invariance yields unambiguous estimates of DOAs, which are then used as coarse references to disambiguate the phase ambiguities in fine estimates induced from the larger spatial invariance. Then, based on the estimated DOAs, another cumulant matrix is derived and decoupled to generate unambiguous and cyclically ambiguous estimates of range parameter. According to the coarse range estimation, the types of sources can be identified and the unambiguous fine range estimates of NF sources are obtained after disambiguation. Compared with some existing algorithms, the proposed algorithm enjoys extended array aperture and higher estimation accuracy. Simulation results are given to validate the performance of the proposed algorithm.

Dan Han, Jin Huang, Jinzhu Zhou et al.

Active electronically scanned array antenna (AESA antenna) is capable of controlling the radiation pattern by controlling the feeding phase of the radiating elements. It has good performance and plays an important role in radar systems. With the development of AESA antenna towards high-frequency bands and high-density arrays, the structural-electromagnetic-thermal (SET) coupling becomes increasingly significant. It seriously restricts the realization of high performances of AESA antennas. However, the previously reported theoretical multi-field-coupled model for the coupling problem ignores the effect of the deformations of the feed system and array elements on the electrical performance. It only considers the positional deviations of the array elements in the coupling field. As a result, the accuracy of the numerical solution by the theoretical model is reduced. To overcome the above problems, this paper first establishes the field-circuit coupling model by introducing the deformation errors of the feed system into the existing theoretical model. Secondly, this paper proposes a new numerical solution for the multi-field-coupled problem of AESA antennas based on model reconstruction. And the model reconstruction includes the following: the NURBS (nonuniform rational B-spline) surface fitting algorithm that completes the mapping from finite element models to geometric models by the surface equations established by the node information and the local model reconstruction algorithm that determines the local geometric models by the positions and the directions. The NURBS surface fitting algorithm guarantees the accuracy of both the positions and shapes of array elements. The local model reconstruction algorithm ensures the accuracy of the amplitudes and phases of feed connectors. Finally, the numerical solution was applied to the 32-element AESA antenna and the simulations are close to the measurements.

Jing Zhang, Xiaoping Liu

Technologies such as Bluetooth, RFID, WiFi, 4G, and the Internet of things are mutually converged with ADSL and fiber to the home network. Users can get information in the forms of word, voice, images, etc. through ubiquitous networks including the fixed telephone, the mobile telephone, the television, the computer, and diversified informational zed terminal equipment. Ubiquity informatization may be the trend of future network development, which is the development direction of the ubiquitous intelligent comprehensive network information society. Its physical representation is the appearance of ubiquitous network or the named universal network. It represents the ubiquitous prosperity that all people, all organizations, and industries can get benefits from the ubiquity informatization. This article studies the internal and external structures of network service model and introduces technology dynamics, demand dynamics, competition, and security as adjustment variables. Then, the evaluation model of network service based on network convergence is proposed and tested. The test results prove the validity of the evaluation model.

Le Huy Trinh, Fabien Ferrero, Leonardo Lizzi et al.

A 4 × 4 MIMO multiband antenna system for mobile handsets is proposed in this paper. The placement of the elements on the terminal chassis as well as the single structure has been optimized in order to reduce the Envelope Correlation Coefficient (ECC). Simulated and measured results, including also the integration with a a real 7-inch commercial tablet, aimed at validating the proposed solution are presented.

Renaud Marti, Simon Gascoin, Thomas Houet et al.

Les bilans de masse des glaciers de montagne constituent des indicateurs climatiques régionaux reconnus. Moyennant une hypothèse sur la densité de la surface glaciaire, on peut établir le bilan de masse d'un glacier par différence entre deux modèles numériques d'élévation (MNE) successifs. L'obtention de MNEs précis à haute résolution est donc un enjeu important en glaciologie. Un couple d'images stéréoscopiques Pléiades acquis en septembre 2013 a été traité afin de générer un MNE du glacier d'Ossoue (Hautes Pyrénées) à 2m de résolution en planimétrie et 1m en altimétrie. Un levé DGPS sur le glacier et sa périphérie à une date proche a permis d'estimer l'erreur altitudinale du MNE Pléiades à ±1.8m. Ce résultat permet d'envisager une utilisation opérationnelle des images stéréoscopiques Pléiades pour déterminer des bilans de masses précis de glaciers de montagne, y compris dans les zones impraticables pour les mesures de terrain.

Laurent Polidori, Elisabeth Simonetto, Eric Labergerie

Malgré le rôle majeur du Prof. Laussedat, considéré comme le père de la photogrammétrie, cette technique n'est apparue au CNAM que dans les années 1930, avec la création de la chaire de Photogrammétrie et le recrutement d'Henri Roussilhe puis Georges Poivilliers. Après 1952, la photogrammétrie a été réservée aux formations de géomètres à Paris, Evry puis Le Mans. Cet article présente l'évolution de l'enseignement de la photogrammétrie au CNAM, des travaux pionniers d'Aimé Laussedat jusqu'à la formation des géomètres en photogrammétrie numérique.

Sonia Fu, Pierre Jacolot, Tommaso Balercia et al.

The contribution focuses on the accuracy of two asymptotic solutions aimed at representing the electromagnetic field scattered by penetrable wedges. One is a heuristic manipulation of the solution for the perfect electrical conductor, and the other one is a more rigorous coefficient based on approximate boundary conditions. The results presented here extend those proposed by other authors by illustrating the accuracy of such solutions at the edge of validity of the uniform theory of diffraction. In particular, they show that the heuristic formulation can be freely applied in similar conditions, while the other might not always lead to accurate predictions.

Xiaoyin Li, Lianshan Yan, Wei Pan et al.

A novel compact coplanar waveguide- (CPW-) fed ultrawideband (UWB) printed planar volcano-smoke antenna (PVSA) with four band-notches for various wireless applications is proposed and demonstrated. The low-profile antenna consists of a C-shaped parasitic strip to generate a notched band at 8.01~8.55 GHz for the ITU band, two C-shaped slots, and an inverted U-shaped slot etched in the radiator patch to create three notched bands at 5.15~5.35 GHz, 5.75~5.85 GHz, and 7.25~7.75 GHz for filtering the WLAN and X-band satellite signals. Simulated and measured results both confirm that the proposed antenna has a broad bandwidth of 3.1~12 GHz with VSWR < 2 and good omnidirectional radiation patterns with four notched-bands.

Siham Hairoud, Pierre Combeau, Yannis Pousset et al.

In order to better assess the behaviours of the propagation channel in a confined environment such as a railway tunnel for subway application, we present an optimization method for a deterministic channel simulator based on 3D ray tracing associated to the geometrical optics laws and the uniform theory of diffraction. This tool requires a detailed description of the environment. Thus, the complexity of this model is directly bound to the complexity of the environment and specifically to the number of facets that compose it. In this paper, we propose an algorithm to identify facets that have no significant impact on the wave propagation. This allows us to simplify the description of the geometry of the modelled environment by removing them and by this way, to reduce the complexity of our model and therefore its computation time. A comparative study between full and simplified environment is led and shows the impact of this proposed method on the characteristic parameters of the propagation channel. Thus computation time obtained from the simplified environment is 6 times lower than the one of the full model without significant degradation of simulation accuracy.

Cai Run-Nan, Yang Ming-Chuan, Lin Shu et al.

A printed director antenna with compact structure is proposed. The antenna is fed by a balanced microstrip-slotline and makes good use of space to reduce feeding network area and the size of antenna. According to the simulation results of CST MICROWAVE STUDIO software, broadband characteristics and directional radiation properties of the antenna are explained. The operating bandwidth is 1.8 GHz–3.5 GHz with reflection coefficient less than −10 dB. Antenna gain in band can achieve 4.5–6.8 dBi, and the overall size of antenna is smaller than 0.34λ0×0.58λ0. Then the antenna is developed to a two-element antenna array, working frequency and relative bandwidth of which are 2.15–2.87 GHz and 28.7%, respectively. Compared with antenna unit, the gain of the antenna array has increased by 2 dB. Thus the proposed antenna has characteristics of compact structure, relatively small size, and wideband, and it can be widely used in PCS/UMTS/WLAN/ WiMAX fields.

Ya Jing, Xu Zhao, Hongwei Kong et al.

With MIMO technology being adopted by the wireless communication standards LTE and HSPA+, MIMO OTA research has attracted wide interest from both industry and academia. Parallel studies are underway in COST2100, CTIA, and 3GPP RAN WG4. The major test challenge for MIMO OTA is how to create a repeatable scenario which accurately reflects the MIMO antenna radiation performance in a realistic wireless propagation environment. Different MIMO OTA methods differ in the way to reproduce a specified MIMO channel model. This paper introduces a novel, flexible, and cost-effective method for measuring MIMO OTA using a two-stage approach. In the first stage, the antenna pattern is measured in an anechoic chamber using a nonintrusive approach, that is without cabled connections or modifying the device. In the second stage, the antenna pattern is convolved with the chosen channel model in a channel emulator to measure throughput using a cabled connection.